nload is a command line tool to measure network usage in real time. nload is a free software by Roland Riegel. nload is very lightweight but it has good interface similar to bwmonitor in Windows. This article tells some examples of nload for personal user need.

To try these commands, make sure you know what network interface you are using by using command ifconfig. For example, I am using WLAN tethering from my smartphone so my interface is wlan0.